Serological diagnostic trial of the causative virus of Bell's palsy by
anti-herpes virus antibodies in the paired sera.
Keiji Chida, M.D.1) and Sadao Takase, M.D.2)
1) Department of Clinical Neurology, National Iwate Hospital
2) Department of Clinical Neurology, Kohnan Hospital
Substantial evidence obtained through polymerase chain reaction techniques strongly supports that reactivation of latently infected herpes simplex virus (HSV) in geniculate ganglia is the main cause of Bell's palsy. However, serum antibody titers to HSV rarely increase in patients with this disease. This discrepancy may result from the difficulty in detecting a small increase in antibody titers by conventional serological analysis. To detect such a small increase in antibody titer, we defined the significant increase in IgG antibody titers more precisely, and examined the association of HSV or varicella-zoster virus (VZV) with Bell's palsy.
From 40 patients with Bell's palsy, paired sera were obtained within the 4 th disease day and 2 weeks later. IgG antibodies to HSV, VZV, cytomegalovirus (CMV), or measles virus (MsV) were measured with solid-phase enzyme immunoassay (EIA). IgM antibodies were measured with captured EIA. Each antibody titer was expressed as an EIA-value, which was quantitatively measured by using a calibration curve prepared from the samples containing known titers to the virus in proportion to the logarithm of its titer. An EIA-value ratio (EVR) between paired sera and a corrected EVR was calculated according to the formulae: EVR= [EIA-value in the second serum] / [EIA-value in the first serum] ;corrected EVR= [EVR to HSV, VZV or CMV] /[EVR to MsV]. The association with a virus was determined to be positive when the corrected EVR of the virus was beyond the normal range (the logarithmical meanŮ3 SD of corrected EVRs among 24 healthy controls) while the corrected EVR of the other viruses were within it. Using the corrected EVR, 6 patients were positive: 4 for HSV, 2 for VZV. On the other hand, the conventional serological analysis, which confirms positivity by a 4-fold increase in IgG antibody titer or a demonstration of IgM antibody, disclosed only 2 positive patients (1 for HSV, 1 for VZV). EIA is a very sensitive method of detecting antibodies. Corrected EVRs can exclude a decrease in antibody titers induced by corticosteroids, which are generally used for therapy of Bell's palsy. Moreover, the normal range of corrected EVRs can be defined more precisely than in conventional serological analyses. Our results indicate that some sensitive analysis, such as the corrected EVR method, may make it possible to serologically detect th e causative virus of Bell's palsy.
(Clinica Neurol, 40: 791-796, 2000)